Elucidating advanced guestbook 2 3 4
There is a noticeable absence of new particle formation as the pollution episode develops, indicating the suppression of nucleation by preexisting particles.
During the transition and polluted periods, a continuous growth from the nucleation mode particles is clearly depicted by the evolution in the mean particle size (Fig.
We illustrate the similarity and difference in particulate matter (PM) formation between Beijing and other world regions.
The periodic cycle of PM events in Beijing is regulated by meteorological conditions.
Although primary emissions by local traffic are clearly discernible by the transiently elevated number concentrations and may play a role in maintaining the particle number concentrations during the polluted period, these primary particles do not appreciably alter the particle mass growth.We demonstrate a periodic cycle of PM episodes in Beijing that is governed by meteorological conditions and characterized by two distinct aerosol formation processes of nucleation and growth, but with a small contribution from primary emissions and regional transport of particles.Nucleation consistently precedes a polluted period, producing a high number concentration of nano-sized particles under clean conditions.The stronger northwesterly and northeasterly winds were most frequent during the clean period, carrying unpolluted air masses from the less populated northern mountainous areas.Furthermore, precipitation typically occurred between the pollution episodes, and wet deposition was also responsible for removal of aerosols.